Iron and steel continue to be essential in today's society. The global steel production has been growing rapidly, from 1248 Mt in 2006 to 1490 Mt in 2011, an increase of about 16% in a short span of 5 years. Steel production is an energy intensive process and thus consumes huge amount of fossil fuels. Each ton of steel production emits 2.2 ton of CO2 as a world average. While, many developed countries discharges 1.8 ton CO2 for 1 ton of steel. Therefore, iron making industries can be seen as one of the biggest targets next to power plants to curb vast emission of greenhouse gases.
There is a need to develop innovative solutions to reduce the emissions from iron and steel industries.
Blast furnaces can produce hot metal iron (Fe) at costs competitive with other iron making technologies, and are predicted to survive through the next millennium. The biggest drawback of blast furnaces is the inevitable production of CO/CO2 gases, as iron is reduced from iron oxide using carbon. For a ton of iron to be made, about 1.5 ton of CO2 gas is emitted into the atmosphere. The conventional approaches of capturing CO2 from blast furnace as add-on technologies (i.e. without any modification of blast furnace) can be broadly classified as: (i) direct capture from blast furnace and (ii) capture after conversion of CO to CO2. Latter approach can provide high CO2 capture rates.
One such conventional method of CO2 absorption at iron industries is through the use of mono ethanol amine (MEA) solution. MEA solvents based absorbents have been criticized because of their low absorption capacity, corrosive nature, and fast degradation of absorption capacity in the presence of exhaust gas. The MEA based chemical absorption method also requires several pretreatment steps in order to strip off undesirable chemical compounds which leads to a very high capture costs, which can be estimated at around $60/ton of CO2. The regeneration of this solution also demands energy and thus eventually results in a high cost and energy intensive process. At the same time, it is evident that the steel industries, being limited by the laws of thermodynamics, have very little left to improve their energy efficiency. Thus, further large reductions in CO2 emissions are not possible just by using existing technologies.
The production of iron and steel will most likely continue to be dependent on the use of fossil fuels for the foreseeable future, and it may not be viable either economically or environmentally. Some background patents include, US Patent Pub. No. 2012/0032378 A1, M. D. Lanyi, J. A. Terrible, entitled “Blast Furnace Iron Production with Integrated Power Generation”; US Patent Pub. No. 2012/0225007 A1, A. A. Park, L. S. Fan, H. R. Kim, entitled “Methods and systems for synthesizing iron-based materials and sequestering carbon dioxide”; and U.S. Pat. No. 4,917,727, H. Hotta, M. Matsuura, Y. Oono, H. Saito, entitled “Method of operating a blast furnace.” Some related publications include, K. Svoboda, G. Slowinski, J. Rogut, D. Baxter. Thermodynamic possibilities and constraints for pure hydrogen production by iron based chemical looping process at lower temperatures, Energy Conversion and Management 48 (2007) 3063-3073 and CO2 capture in industries and distributed energy systems: possibilities and limitations, Takeshi Kuramochi, 2011.